Electrochemical synthesis of ammonia in alkaline media

ABSTRACT

A method is provided for an electrochemical synthesis of ammonia in alkaline media. The method electrolytically converts N 2  and H 2  to NH 3  in an electrochemical cell comprising an anode, a cathode, and an alkaline electrolyte. The method includes exposing an anode to a H 2 -containing fluid, wherein the anode is active toward adsorption and oxidation of H 2 ; exposing a cathode to a N 2 -containing fluid, wherein the cathode is active toward adsorption and reduction of N 2  to form NH 3 ; and applying a voltage between the anode and the cathode so as to facilitate adsorption of hydrogen onto the anode and adsorption of nitrogen onto the cathode; wherein the voltage is sufficient to simultaneously oxidize the H 2  and reduce the N 2 . The electrolytic method is performed with the H 2  and N 2  pressures from about 10 atmospheres (atm) to about 1 atm; and at temperatures from about 25° C. to about 205° C.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a submission under 35 USC §371 of InternationalApplication No. PCT/US2014/031887, filed Mar. 26, 2014, which claimspriority to Provisional Application No. 61/805,366 filed Mar. 26, 2013,the disclosures of which are expressly incorporated herein by referencein their entirety.

FIELD OF THE INVENTION

The invention relates generally to the electrochemical synthesis ofammonia in alkaline media.

BACKGROUND

One of the most widely produced chemicals worldwide is ammonia, whichhas applications as a fertilizer, a hydrogen storage media, and as areactant in selective catalytic reduction of combustion gases fromvehicles and stationary facilities, amongst many others.

The Haber (or Haber-Bosch) process is the principle manufacturing methodfor synthesizing ammonia. In the Haber process, ammonia is synthesizedfrom nitrogen and hydrogen gas according to the following reaction:N₃+3H₂→2NH₃  Equation (1)The Haber process employs an iron-based catalyst and operates at hightemperatures (e.g., above about 430° C. (about 806° F.)) and highpressures (e.g., above about 150 atmospheres (about 2,200 pounds persquare inch)), which lead to high-energy consumption. In addition, theammonia conversions are relatively low, e.g., between about 10% andabout 15%.

Due to these extreme process limitations, several researchers haveinvestigated the synthesis of ammonia through an electrochemicalapproach. However, thus far, all the electrochemical routes presented inthe literature had been performed in the solid state, which implies theuse of solid and/or composite electrolytes. Therefore, the transport ofthe ions is limited by temperature. The electrochemical reactionsreported in the literature are based on the transport of protons inwhich the reduction of nitrogen takes place according to:N₂+6H⁺+6e ⁻→2NH₃  Equation (2)while the oxidation of hydrogen takes place according to:3H₂→6H⁺+6e ⁻  Equation (3)

Operating temperatures in the different systems that have been describedin the literature range from 480° C. to 650° C., using perovskite-type,pyrochlore-type, and fluorite-type solid-state proton conductors aselectrolytes. In addition to the high operating temperatures, theammonia formation rates are low, with the highest reported rate in theorder of 10⁻⁵ mol/s m². Lower temperatures have been achieved with theuse of Nafion®-type membranes allowing ammonia formation rates in theorder of 1×10⁻⁴ mol/s m² at 80° C. to 90° C. However, the operatingvoltages for the cell are high, in the order of 2.0 V, which representsa high energy consumption for the synthesis.

In view of the foregoing, there is a need for new methods forsynthesizing ammonia.

SUMMARY

The present invention overcomes one or more of the foregoing problemsand other shortcomings, drawbacks, and challenges of conventionalammonia synthesis. While the invention will be described in connectionwith certain embodiments, it will be understood that the invention isnot limited to these embodiments. To the contrary, this inventionincludes all alternatives, modifications, and equivalents as may beincluded within the scope of the present invention.

According to an embodiment of the present invention, a method forelectrolytically converting molecular nitrogen (N₂) to ammonia (NH₃) inan electrochemical cell comprising an anode, a cathode, and an alkalineelectrolyte is provided. The method comprises exposing an anodecomprising a first conducting component to a molecular hydrogen (H₂)containing fluid at a first pressure and first temperature, wherein thefirst conducting component is active toward adsorption and oxidation ofH₂; exposing a cathode comprising a second conducting component to amolecular nitrogen (N₂) containing fluid at a second pressure and secondtemperature, wherein the second conducting component is active towardadsorption and reduction of N₂ to form NH₃; and applying a voltagebetween the anode exposed to the H₂-containing fluid and the cathodeexposed to the molecular N₂-containing fluid so as to facilitateadsorption of hydrogen onto the anode and adsorption of nitrogen ontothe cathode; wherein the voltage is sufficient to simultaneously oxidizethe H₂ and reduce the N₂. The electrolytic method is further performedwith the first and second pressures independently equal to or less thanabout 10 atmospheres (atm) to about 1 atm; and with the first and secondtemperatures greater than about 25° C. and less than about 205° C.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the presentinvention and, together with a general description of the inventiongiven above, and the detailed description of the embodiments givenbelow, serve to explain the principles of the present invention.

FIG. 1 is a diagrammatical view of a simplified electrolytic cellconfigured for flow cell processing, in accordance with an embodiment ofthe present invention;

FIG. 2 is a graph of voltage (volts) versus temperature (degreesCelcius) showing theoretical operating cell voltage at differenttemperatures and 1 atm to favor the production of ammonia, in accordancewith an embodiment of the present invention;

FIG. 3 is a perspective diagrammatical view of a simplifiedelectrochemical cell assembly configured for batch processing, inaccordance with another embodiment of the present invention; and

FIG. 4 is a polarization curve of voltage (volts) versus time (seconds)for the synthesis of ammonia at 5 mA and 25° C., in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

An electrochemical method and apparatus for synthesizing ammonia in analkaline media are disclosed in various embodiments. However, oneskilled in the relevant art will recognize that the various embodimentsmay be practiced without one or more of the specific details or withother replacement and/or additional methods, materials, or components.In other instances, well-known structures, materials, or operations arenot shown or described in detail to avoid obscuring aspects of variousembodiments of the present invention.

Similarly, for purposes of explanation, specific numbers, materials, andconfigurations are set forth in order to provide a thoroughunderstanding. Nevertheless, the embodiments of the present inventionmay be practiced without specific details. Furthermore, it is understoodthat the illustrative representations are not necessarily drawn toscale.

Reference throughout this specification to “one embodiment” or “anembodiment” or variation thereof means that a particular feature,structure, material, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention, butdoes not denote that they are present in every embodiment. Thus, theappearances of the phrases such as “in one embodiment” or “in anembodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the invention.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments. Various additional layers and/or structures may be includedand/or described features may be omitted in other embodiments.

Additionally, it is to be understood that “a” or “an” may mean “one ormore” unless explicitly stated otherwise.

Various operations will be described as multiple discrete operations inturn, in a manner that is most helpful in understanding the invention.However, the order of description should not be construed as to implythat these operations are necessarily order dependent. In particular,these operations need not be performed in the order of presentation.Operations described may be performed in a different order than thedescribed embodiment.

Various additional operations may be performed and/or describedoperations may be omitted in additional embodiments.

FIG. 1 is a diagrammatic depiction of a simplified electrochemical cell10 configured for flow cell processing to achieve convert molecularnitrogen (N₂) to ammonia (NH₃). The simplified electrochemical cell 10comprises a cathodic chamber 15 containing a cathode electrode 20, ananodic chamber 25 containing an anode electrode 30, wherein the cathodicchamber 15 and the anodic chamber 25 are physically separated from eachother by a separator 35. However, while also serving as a physicalbarrier between the cathode electrode 20 and the anode electrode 30, theseparator 35 allows the transport of ions between the cathodic chamber15 and the anodic chamber 25. The cathode electrode 20 and the anodeelectrode 30 are configured with an electrical connection therebetweenvia a cathode lead 42 and an anode lead 44 along with a voltage source45, which supplies a voltage or an electrical current to theelectrochemical cell 10.

The cathodic chamber 15 comprises an inlet 50 by which a nitrogen (N₂)containing fluid enters and an outlet 55 by which ammonia (NH₃) andunreacted nitrogen exit. Similarly, the anodic chamber 25 comprises aninlet 60 by which a hydrogen (H₂) containing fluid enters and an outlet65 by which water vapor and unreacted hydrogen exit. Each of thecathodic and anodic chambers 15, 25 may further comprise gas distibutors70, 75, respectively. The electrochemical cell 10 may be sealed at itsupper and lower ends with an upper gasket 80 and a lower gasket 85.

In accordance with embodiments of the present invention, the cathodeelectrode 20 comprises a substrate and a conducting component that isactive toward adsorption and reduction of N₂. At the cathode electrode20 the reduction of nitrogen gas to ammonia takes place according to thefollowing reaction:N₂+6H₂O+6e ⁻→2NH₃+6OH⁻  Equation (4)The reduction reaction of nitrogen gas shown in Equation (4) takes placeat a theoretical potential of −0.77 V vs. standard hydrogen electrode(SHE). Therefore, in order to favor the conversion of nitrogen toammonia potentials more negative than −0.77 V vs. SHE must be applied,while minimizing the water reduction reaction (which takes place atpotentials equal or more negative than −0.82 vs. SHE).

In accordance with embodiments of the present invention, the substratemay be constructed of high surface area materials so as to increase theavailable surface area for the cathodic conducting component.Additionally, the substrate may be compatible with an alkaline media,i.e., the alkaline electrolyte. As used herein, “alkaline” means the pHof the media or electrolyte is at least about 8. For example, the pH maybe 9, 10, 11, 12, or more. Non-limiting examples of suitable substratesinclude conductive metals, carbon fibers, carbon paper, glassy carbon,carbon nanofibers, carbon nanotubes, nickel, nickel gauze, Raney nickel,alloys, etc. The selected substrate should be compatible with thealkaline media or electrolyte.

In accordance with embodiments of the present invention, the cathodeelectrode substrate is coated with a conducting component, which is amaterial that is active for the adsorption and reduction of nitrogenaccording to Equation (4). Active catalysts include metals such asplatinum (Pt), iridium (Ir), ruthenium (Ru), palladium (Pd), rhodium(Rh), nickel (Ni), iron (Fe), copper (Cu), and their combinations. Whena combination of one or more metals is used for the conducting componentof the cathode electrode 20, the metals can be co-deposited as alloys asdescribed in U.S. Pat. Nos. 7,485,211 and 7,803,264, and/or by layers asdescribed in U.S. Pat. No. 8,216,956, wherein the entirety of thesedisclosures are incorporated by reference herein in their entirety. Inone embodiment, where the metals are layered, the overlying layer ofmetal may incompletely cover the underlying layer of metal.

Water is a reactant consumed in the reduction reaction of nitrogen toform ammonia. Accordingly, the surface of the cathode electrode 20should stay wet. One suitable manner to provide a sufficient degree ofhumidity to the nitrogen containing gas is to pass the gas through ahumidifier. However, in order to minimize the reduction of water,nitrogen should be in excess when compared to the water (see Equation(2) for the reduction of water, which takes place at −0.82 v vs. SHE).If water is used in excess relative to nitrogen, the undesirablereduction of water (see Equation (5)) may compete with or suppress theintended reduction of nitrogen in the formation of ammonia (see Equation(1)).2H₂O+2e ⁻→2OH⁻+H₂  Equation (5)The excess or unreacted nitrogen gas that exits the cathodic chamber 15can be separated from the ammonia product and recirculated in theprocess.

Nitrogen feedstock is not particularly limited to any source and may besupplied to the nitrogen containing fluid as a pure gas and/or from air,which is approximately 80% nitrogen. Other inert gases (e.g., a carriergas) can be present in the nitrogen containing fluid. Carbon dioxide maypoison the cathodic reduction catalyst, so it should be avoided orminimized in the nitrogen-containing fluid. In one embodiment, purenitrogen is used as the nitrogen containing fluid. In anotherembodiment, air, which has been passed through a carbon dioxidescrubber, is used as the nitrogen containing fluid.

To enhance the distribution of nitrogen in the cathodic chamber 15, thegas distributor 70 (e.g., screen of metals) provides channels for thenitrogen to disperse and contact the cathode 20. Wet proofing materialssuch as polytetrafluoroethylene (PTFE) can be included in the electrodestructure (e.g., rolled, added as a thin layer) to control thepermeation of the alkaline electrolyte through the electrode andminimize flooding.

In accordance with embodiments of the present invention, the anodeelectrode 30 comprises a substrate and a conducting component that isactive toward adsorption and oxidation of hydrogen. At the anodeelectrode 30, the oxidation of hydrogen gas in an alkaline media orelectrolyte takes place according to the following reaction:3H₂+6OH⁻→6H₂O+6e ⁻  Equation (6)

The hydrogen oxidation reaction shown in Equation (6) takes place at atheoretical potential of −0.82 V vs. standard hydrogen electrode (SHE).Therefore, in order to favor the conversion of hydrogen, potentials morepositive than −0.82 V vs. SHE must be applied.

In accordance with embodiments of the present invention, the anodeelectrode substrate may be constructed of a high surface area materialso as to increase the available surface area for the anodic conductingcomponent. Additionally, the anode electrode substrate may be compatiblewith an alkaline media, i.e., the alkaline electrolyte. Non-limitingexamples of suitable substrates include conductive metals, carbonfibers, carbon paper, glassy carbon, carbon nanofibers, carbonnanotubes, nickel, nickel gauze, Raney nickel, alloys, etc. The selectedsubstrate should be compatible with the alkaline media or electrolyte.

In accordance with embodiments of the present invention, the anodeelectrode substrate is coated with a conducting component, which is amaterial that is active for the adsorption and oxidation of hydrogenaccording to Equation (6). Active catalysts include metals such asplatinum (Pt), iridium (Ir), ruthenium (Ru), palladium (Pd), rhodium(Rh), nickel (Ni), iron (Fe), and their combinations. When a combinationof one or more metals is use for the conducting component of the anodeelectrode 30, the metals can be co-deposited as alloys and/or by layers,as described above. In one embodiment, where the metals are layered, theoverlying layer of metal may incompletely cover the underlying layer ofmetal.

In accordance with embodiments of the present invention, a hydrogencontaining fluid is the preferred reacting chemical in the anodicchamber 25. Other inert gases (e.g., a carrier gas) can be present inthe hydrogen containing fluid mixture. In one embodiment, pure hydrogenis used as the hydrogen containing fluid. The excess hydrogen gas can berecirculated in the process.

Gas distribution channels (e.g., screen of metals) can be added to theanodic chamber to enhance the distribution of the gas among the anodicchamber 25. Wet proofing materials such as polytetrafluoroethylene(PTFE) can be included in the electrode structure (rolled, added as athin layer) to control the permeation of the electrolyte through theelectrode and avoid flooding.

In accordance with embodiments of the present invention, an alkalineelectrolyte is used in the electrochemical cell 10. The electrolyte maybe a liquid and/or a gel electrolyte. Examples of electrolytes includehydroxide salts, such as potassium hydroxide (KOH) or sodium hydroxide(NaOH), or mixtures of hydroxide salts and polyacrylic acid gels, suchas KOH/polyacrylic acid gel. The electrolyte may flow through the cellor be used as a stationary media or coating. The pH of the alkalineelectrolyte may be about 8 or greater. For example, an alkalineelectrolyte comprising an aqueous solution of a hydroxide salt may havea concentration of the hydroxide salt from about 0.5 M to about 9 M. Inone example, the alkaline electrolyte comprises a 5 M solution of KOH.Additionally, other alkaline electrolytes may be used provided that theyare compatible with the catalysts, do not react with the hydrogen,nitrogen, and ammonia, and have a high conductivity.

In accordance with another embodiment, when present, the separator 35may divide the cathodic and anodic chambers 15, 25, and physicallyseparate the cathode electrode 20 and the anode electrode 30. Exemplaryseparators include anion exchange membranes and or thin polymeric filmsthat permit the passage of anions.

In accordance with embodiments of the present invention, theelectrochemical cell 10 can be operated at a constant voltage or aconstant current. While the electrochemical cell 10 in FIG. 1 is shownin a flow cell configuration, which can operate continuously, thepresent invention is not limited thereto. For example, theelectrochemical ammonia synthesis process in accordance with anotherembodiment of the present invention may be conducted in a batchconfiguration.

The overall electrolytic cell reaction for the synthesis of ammonia fromnitrogen and hydrogen is given by Equation (1). Therefore, the appliedcell voltage at standard conditions (Temperature=25° C., and Pressure=1atm) should be equal to or lower than about 0.059 V to favor thesynthesis of ammonia. The value of the applied voltage varies with thetemperature, for example at about 205° C. the applied voltage may beequal to or lower than about −0.003 V (where the cell transitions fromgalvanic at 25° C. to electrolytic at 205° C.). In accordance withembodiments of the present invention, the pressure of the cell can be ina range from about 1 atm to about 10 atm.

EXAMPLES Example 1 Operating Cell Voltage

FIG. 2 presents a plot of the theoretical operating cell voltage, atdifferent temperatures and at 1 atm of pressure, which favors theproduction of ammonia. As shown in FIG. 2, at temperatures above 195°C., the electrochemical cell 10 transitions from a galvanic cell(positive voltage) to an electrolytic cell (negative voltage). Inaccordance with embodiments of the present invention, the appliedpotential to favor the production of ammonia should be equal to or morenegative than the thermodynamic voltage (as indicated in FIG. 2). Thus,in accordance with an embodiment, the electrochemical method of formingammonia includes maintaining the voltage equal or more negative than atemperature dependent thermodynamics voltage for the production ofammonia. The higher the overpotential (difference between thethermodynamics potential shown in FIG. 2 and the applied cell voltage)the lower the faradaic efficiency for the production of ammonia, due tothe hydrogen evolution reaction shown in Equation 2.

Example 2 Ammonia Synthesis

An electrochemical cell assembly 100 for demonstrating the synthesis ofammonia, in accordance with an embodiment of the present invention, isshown in FIG. 3. The electrochemical cell 10 of FIG. 1 can be fluidlycoupled to two columns, which are used for the collection of gases byliquid displacement. In this batch configuration, the anode column 110contains a solution of 5 M KOH, while the cathode column 120 contains asolution of 5 M KOH/1 M NH₃. Each of the columns 110, 120 comprise anupper chamber (110 a, 120 a), a lower chamber (110 b, 120 b), and adivider plate 125, 130. The upper (110 a, 120 a) and lower (110 b, 120b) chambers are fluidly coupled with a displacement tube 135, 140,respectively, which permits displacement of liquid therebetween. Thelower chamber 110 b of anode column 110 is fluidly coupled to the inlet60 and outlet 65. The lower chamber 120 b of cathode column 120 isfluidly coupled to the inlet 50 and the outlet 55. The cathode electrode20 and the anode electrode 30 may be constructed from carbon paperelectrodes that are electroplated with Pt—Ir, which may be co-depositedby following the procedures described in U.S. Pat. Nos. 7,485,211 and7,803,264, to provide a loading of 5 mg/cm². The electrodes may beseparated by a Teflon membrane, which allows the transport of OH⁻ ions.

Prior to applying current to the electrochemical cell 10, the lowerchambers 110 b, 120 b are substantially filled with their respectiveelectrolyte solutions, which substantially fills the cathodic chamber 15and the anodic chamber chamber 25 of the electrochemical cell 10. Uponapplication of reversed polarity potential to the electrodes, whicheffectively inverts the cathode and the anode electrodes, electrolysisof ammonia to form hydrogen and nitrogen is performed, as described inU.S. Pat. No. 7,485,211. More specifically, 1) hydrogen (H₂) gas isgenerated in chamber 25 and displaces a portion of the 5 M KOHelectrolyte contained in lower chamber 110 b into upper chamber 110 a;and 2) nitrogen (N₂) gas is generated in chamber 15 and displaces aportion of the 5 M KOH/1 M NH₃ contained in lower chamber 120 b intoupper chamber 120 a.

Accordingly, in a first phase, a constant current of 100 mA (of invertedpotential) was applied to the electrochemical cell 10 and theelectrolysis of ammonia to form N₂ and H₂ was performed. The temperatureof the cell was kept at ambient temperature (25° C.). The electrolysisexperiment was performed until about 15 ml of H₂ gas and about 5 ml ofN₂ gas were collected in the two chambers 110 b, 120 b, as shown in FIG.3. Under these conditions the cell operated as an electrolytic cell.

After sufficient volumes of hydrogen (15 ml) and nitrogen (5 ml) gaswere produced, the polarity of the cell was reversed, and a current of 5mA was drawn from the cell at ambient temperature (25° C.). FIG. 4 showsthe results of the polarization of the cell at 5 mA. After approximately14 minutes of operation, the H₂ and the N₂ in the different compartments110 b, 120 b of the electrochemical cell 10 were consumed according tothe stoichiometry described in Equation (4), indicating the feasibilityof the synthesis of ammonia. The voltage in the cell decreased as afunction of time. Without being bound by any particular theory, it ishypothesized that the observed drop in the cell voltage of the ammoniasynthesis cell was caused by a less than optimal contact of thegases/electrolyte with the electrodes of the cell and by the consumptionof the reactants (N₂ and H₂). As the gases were consumed, the cellvoltage turned to a negative value favoring the reverse reaction toEquation (4), which is also known as ammonia electrolysis.

Example 3 Yield and Faradaic Efficiency

Based on the current drawn during the synthesis of ammonia (5 mA), theammonia production rate is estimated at 1.06×10⁻³ g/hr, while thetheoretical amount that could have been produced based on the hydrogenconsumption in the first 14 minutes of the reaction is 2.98×10⁻² g/hr,which represents an ammonia yield of about 3.5%.

The ammonia production rate of 1.73×10⁻⁴ mol/s m² (at the low voltageshown in FIG. 4) is higher than any other value reported in theliterature, e.g., 1.13×10⁻⁴ mol/s m² at 2 V was obtained using protonconduction in a solid-state electrochemical cell, as reported in R. Liu,G. Xu, Comparison of Electrochemical Synthesis of Ammonia by UsingSulfonated Polysulfone and Nafion Membrane with Sm_(1.5)Sr_(0.5)NiO₄ ,Chinese Journal of Chemistry 28, 139-142 (2010). The observed high yieldof ammonia is surprising at the low operating temperatures and pressuresof the present method. The Haber-Bosch process requires 500° C. and150-300 bar for the synthesis of ammonia with a yield of 10-15%.

While the present invention has been illustrated by the description ofone or more embodiments thereof, and while the embodiments have beendescribed in considerable detail, they are not intended to restrict orin any way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. The invention in its broader aspects is thereforenot limited to the specific details, representative apparatus and methodand illustrative examples shown and described. Accordingly, departuresmay be made from such details without departing from the scope of thegeneral inventive concept.

What is claimed is:
 1. A method for electrolytically convertingmolecular nitrogen (N₂) to ammonia (NH₃) in an electrochemical cellcomprising an anode, a cathode, and an alkaline electrolyte, the methodcomprising: exposing an anode comprising a first conducting component toa molecular hydrogen (H₂) containing fluid at a first pressure and firsttemperature, wherein the first conducting component is active towardadsorption and oxidation of H₂; exposing a cathode comprising a secondconducting component to a molecular nitrogen (N₂) containing fluid at asecond pressure and second temperature, wherein the second conductingcomponent is active toward adsorption and reduction of N₂ to form NH₃;and applying a voltage between the anode exposed to the H₂-containingfluid and the cathode exposed to the molecular N₂-containing fluid so asto facilitate adsorption of hydrogen onto the anode and adsorption ofnitrogen onto the cathode; wherein the voltage is sufficient tosimultaneously oxidize the H₂ and reduce the N₂; wherein the first andsecond pressures are independently equal to or less than about 10atmospheres (atm) to about 1 atm; and wherein the first and secondtemperatures are greater than about 25° C. and less than about 205° C.2. A method according to claim 1, further comprising maintaining thevoltage equal or more negative than a temperature dependentthermodynamics voltage for the production of ammonia.
 3. The method ofclaim 1, wherein the voltage is applied as a constant voltage.
 4. Themethod of claim 1, wherein the first conducting component of the anodecomprises a metal selected from platinum, iridium, ruthenium, palladium,rhodium, nickel, iron, or a combination thereof.
 5. The method of claim4, wherein the first conducting component of the anode comprises acombination of the metals, which are co-deposited as alloys or depositedby layers.
 6. The method of claim 1, wherein the second conductingcomponent of the cathode comprises a metal selected from platinum,iridium, ruthenium, palladium, rhodium, nickel, iron, copper, or acombination thereof.
 7. The method of claim 6, wherein the secondconducting component of the cathode comprises a combination of themetals, which are co-deposited as alloys or deposited by layers.
 8. Themethod of claim 1, wherein the alkaline electrolyte has a pH equal to orgreater than about
 8. 9. The method of claim 1, wherein the alkalineelectrolyte comprises a hydroxide salt.
 10. The method of claim 1,wherein the alkaline electrolyte comprises an alkali metal or alkalineearth metal salt of a hydroxide.
 11. The method of claim 1, wherein thealkaline electrolyte has a hydroxide concentration from 0.1 M to about 9M.
 12. The method of claim 1, wherein the alkaline electrolyte containspotassium hydroxide in a concentration from about 0.1 M to about 9 M.13. The method of claim 9, wherein the alkaline electrolyte furthercomprises a polymeric gel.
 14. The method of claim 13, wherein thepolymeric gel comprises a polyacrylic acid.
 15. The method of claim 1,wherein the electrochemical cell further comprises a separator.
 16. Themethod of claim 15, wherein separator comprises an anion exchangemembrane.